1. Field of the Invention
The field of the present invention relates generally to devices for use in lifting objects. In particular, the present invention relates to portable pneumatically-operated lifting devices. Even more specifically, the present invention relates to low profile portable pneumatic jacks that utilize one or more pressurizable bellows.
2. Background
The most commonly available jacking system currently used today are mechanical jacking devices that require the user to place the jack under the object to be lifted, such as one side or end of a motor vehicle, and mechanically operate the jack to extend the lifting axis and raise the object. Mechanical jacking devices have a number of commonly known disadvantages, including lack of stability and strength and the requirement of mechanical effort on part of the user. Another disadvantage of mechanical lifting devices is the amount of space required for the user to effectively utilize the mechanical jack. The space requirement limits the usefulness of these devices in situations where there is not much room for the user to operate the mechanical jack.
Pneumatic jacks overcome many of the limitations of mechanical jacking devices and are commonly used to lift various objects in many different situations. A number of such jacks are portable to allow use at locations other than at fixed facilities, such as repair workshops or garages. One common use for portable pneumatic jacks is to lift one side or end of a motor vehicle or trailer off the ground surface to enable a person to replace a damaged tire or get under the motor vehicle to perform other repair work. For such use, the unextended pneumatic jack must have a low profile to allow the user to easily place the jack under the disabled vehicle. Once placed under the portion of the vehicle the user desires to raise, air or hydraulic fluid is directed toward the jack to extend it and raise the vehicle. In general, pneumatic jacks are suitable for lifting relatively heavy objects without requiring an undue amount of space or effort on part of the jack user.
A number of low profile pneumatic jacks are known. The known pneumatic jacks generally utilize a telescopically extendable lifting axis that extends in response to the introduction of air or hydraulic fluid into the jack. These type of jacks have a number of disadvantages, including known problems with the telescopic member sticking or even jamming during lifting or lowering operations.
Pneumatic jacks that rely on a telescoping member to obtain the desired lift have an inherent limit on the maximum amount of lift that can be obtained. The maximum lift of these type of pneumatic jacks is limited by the design of the telescoping member. A pneumatic jack that relies on flexible bellows for lift, such as the present invention, is not so limited. Although this could have some benefits in certain situations, the ability of the jack to obtain very high lift can result in an overturned vehicle or other object that is being lifted. To prevent over-filling and the potential for such problems, pneumatic jacks often incorporate an automatic pressure release valve that vents pressurized air to the atmosphere. Unfortunately, persons have been known to attempt to overcome the JACK automatic pressure release valves (i.e., by blocking the release port or other means) in order to obtain lift that is outside the range in which the pneumatic jack is designed.
3. Related Art
A number of related art devices exist that identify themselves as pneumatic or air-controlled lift devices. Such devices include U.S. Pat. No. 3,730,481 to Ekonen, U.S. Pat. No. 3,743,248 to Moor, U.S. Pat. No. 3,751,007 to Hollerith, U.S. Pat. No. 3,993,286 to Greene, U.S. Pat. No. 4,021,018 to Dasan, and U.S. Pat. No. 4,913,402 to McJunkin. None of these related art devices solve the problems identified and solved by the present invention in the manner solved by the present invention. Each of the aforementioned patents present pneumatic jacks that utilize a telescoping member. Only the Moor patent discloses the use of a bellows in conjunction with a low profile, portable pneumatic jack. The rubber bellows in the Moore patent, shown as 28 in FIG. 1 therein, merely serves as a casing to enclose the telescoping member and protect it against soiling and damage.